End-stage renal disease is a global epidemia with an estimated incidence of 7% per year and high morbidity-mortality rate. Early detection of chronic kidney disease (CKD) and intervention for CKD complication is important to retard renal progression. However, "traditional uremic toxin" or "small water-soluble molecules" are poorly correlated with the renal function, uremic symptoms and outcomes of CKD patients.

Information of p-cresol in CKD patients is not available. The investigators hypothesized p-cresol can be accumulated in early CKD and have a positive correlation with the morbidity- mortality of CKD patients.

Value of p-cresol in different stages of CRF is still unknown. Information of p-cresol in CKD patients is not available. The investigators hypothesized p-cresol can be accumulated in early CKD and have a positive correlation with the morbidity- mortality of CKD patients.

The principal aim of this prospective cohort study is to investigate the association between total serum levels of p-cresol and the glomerular filtration rate. The correlation of level of p-cresol and morbidity-mortality in CKD patients will be also evaluated.

To determine the relationship, patients of nephrology clinic with a diagnosis of CKD were enrolled in this prospective study and follow-up for 1-year period. The association between total and free serum levels of p-cresol and the glomerular filtration rate were evaluated in CKD patients. The p-cresol level was correlated with other many inflammatory markers (white blood cell counts, ferritin, hs-crp, leptin) and also with the hospitalization rate secondary to cardiovascular and infectious event. The renal outcome and all-cause mortality was assessed. Determination of this relationship can help to establish an accurate marker for early detection of CKD and also its prognostic role in CKD patients.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT00888030